I replaced the 5 XLR cables connecting the Pre to the Amp with RCAs, and now everything is as it should be. Honestly, I don't know what could have caused this, but I'm not going to worry too much about it. I use very short runs of cable (less than 3 feet), so it would seem there is no advantage to XLR over RCA anyway.

Either I had a faulty cable, or there is some incompatibility between my Pre and my Amp. I'm leaning toward the latter. I found an interesting passage in the Marantz 8801 manual here:

Quote:

AV8801 BALANCED XLR PRE OUT terminal PIN arrangement:

1 GND (Ground)2 HOT (+)3 COLD (–)The PIN arrangement in this device uses the European method.In the USA method, 2 is COLD, and 3 is HOT.When connecting a device that utilizes the USA type of PIN arrangement, replacethe 2 and 3 plugs on one side of the balanced cable.

This seems crazy to me! So rather than spend any more time on it, I'm just going to be happy with my unbalanced RCA connections and leave it at that! But again, if anyone has any insight, I would be interested to hear it. Thanks again!

Lee, so the bottom line is that there appears to be incorrect wiring in either one of the Marantz XLR output channels, one of the Sunfire XLR input channels, or one of the BlueJeans XLR cables connecting them. Whichever may be the case, there's already been more than enough concern exercised, so just relax and enjoy the better sound. The coaxial connection is totally sufficient.

The balanced XLR connection is only of benefit in reducing noise in primarily professional applications where there's both a high level of electrical interference and long runs occur through it. Most home setups, undoubtedly including yours, don't experience an interference problem with regular shielded coaxial cables. Reports of substantial XLR benefits, not relating to just noise rejection, exist on some audio forums, but if the equipment used didn't compensate for the double voltage(by having 6dB less gain in the XLR circuitry), causing an increase in loudness at the same setting, this is simply another example of louder sounding better.

Incidentally, both the Marantz and Sunfire units are designed to use the standard pin2 positive convention. Also, the quote from the Marantz manual regarding supposed "methods" is incorrect or at best, outdated. For the correct info on this point, see Bob Lee's discussion here .

Interesting! Thanks for clearing that up for me, John. I will certainly just kick back and enjoy the status quo. Out of curiosity, is there a way to open up the XLR cables and check the polarity myself? I'm trying to decide if I should send them back to Blue Jeans to be tested (at my expense if there's nothing wrong with them!).